Computer hesitates

I have a HP Pavilion Media Center m8330f Desktop PC, running Windows 8.1 Pro, 64-bit with 6 gb of memory. Nothing else special about it. When I first installed windows, I had problems with the system hanging and discovered that I needed to get a new driver for my USB wireless antenna. Since then it has run 1,000% better. However, now it "hesitates". Don't know how else to describe it. If I play a card game, I will be moving along and then I click on a card to move it and find that the system froze for a second and won't allow me to move. Then, just a short second later, it goes back to normal. I have checked device manager and gone through every device. No yellow warnings or driver problems that I can see. On this one, I'm not even sure where to start looking.
I don't think this has anything to do with it, although it might. When I first turn on the machine, unlike every other system where I loaded up Windows 8, the system whirs and whines (hard disc noise, almost like it is looking for a file but can't find it but no error messages) for about 10 seconds with the blue screen and the little white circle. Then screens go blank, and it is like the system has rebooted. Blue screen and white circle reappear and it loads up fine. I think this is caused by the HP system running its POST and loading up its junk before it allows Windows 8 to take over, but have no way of checking if that is the case. Doesn't seem to bother anything once it boots up. Only problem after that is the hesitation.